ATA6602 ATMEL Corporation, ATA6602 Datasheet - Page 16

• Manufacturer Part Number: ATA6602
• Description: LIN and Microcontroller System-In-Package: LIN Transceiver, integrated 5V/50 mA voltage regulator, window watchdog and automotive AVR ATmega88 (8 kBytes Flash); green QFN48 package.
• Manufacturer: ATMEL Corporation

3.3.17.2
16
ATA6602/ATA6603
Worst Case Calculation with R
troller after t
signal from the microcontroller is anticipated within the time frame of t
triggering from glitches, the trigger pulse must be longer than t
restart the watchdog sequence. Should the triggering signal fail in this open window t
NRES output will be drawn to ground after t
causes NRES to immediately switch low.
Figure 3-9.
The internal oscillator has a tolerance of ±20%. This means that t
The worst case calculation for the watchdog period T
calculated as follows.
The ideal watchdog time T
t
t
T
T
T
A microcontroller with an oscillator tolerance of ±15% is sufficient to supply the trigger inputs
correctly within the time period of T
1,min
2,min
wdmax
wdmin
wd
V
DD
NTRIG
PTRIG
= 14.2 ms ±2.2 ms (±15%)
NRES
= 0.8
= 0.8
= 5V
= t
= t
1max
1min
d
t
t
= 49 ms. The times t
1
2
+ t
= 12 ms
Timing Sequence with R
t
Undervoltage Reset
= 8 ms, t
= 8.4 ms, t
reset
2min
WO_OSC
= 10 ms
= 8 ms + 8.4 ms = 16.4 ms
1,max
= 51 k
2,max
wd
= 1.2
is between (t
= 1.2
t
d
1
= 49 ms
wd
and t
t
1
= 14.2 ms (±15%) in an application with R
t
= 12 ms
WD_OSC
2
t
2
= 12.6 ms
1
1
have a fixed relationship with each other. A triggering
= 10 ms
maximum) and (t
t
2
trigg
. A triggering signal during the closed window t
= 51 k
t
> 3 µs
wd
t
2
= 10.5 ms
wd
the microcontroller has to provide is
1
minimum plus t
trigg
t
1
1
and t
> 3 µs. This slope serves to
2
= 10.5 ms. To avoid false
2
can also vary by ±20%.
t
2
2
minimum).
wd_osc
Watchdog Reset
4921C–AUTO–01/07
t
nres
= 51 k .
= 1.9 ms
2
, the
1